start()
Attempts to start the query.
Declaration
func start() -> BoolReturn Value
true when successful; otherwise, false.
A query may fail to start if it does not specify a predicate, or if the query has already been started.
Discussion
A query can’t be started if the receiver is already running a query or no predicate has been specified.
This method must be called from the receiver’s operationQueue or on the main thread. For example: